Certain 1-phenyl-3-alkyl-1,3-propanediones

ABSTRACT

Compounds of the formula ##STR1## wherein R is halogen; C 1  -C 2  alkyl; C 1  -C 2  alkoxy; nitro; cyano; C 1  -C 2  haloalkyl; or R a  SO n  -- wherein n is 0 or 2 and R a  is C 1  -C 2  alkyl; R 1  is C 1  -C 4  alkyl; R 2  is C 1  -C 4  alkyl or C 1  -C 4  alkoxy; R 3  and R 4  independently are (1) hydrogen; (2) halogen; (3) C 1  -C 4  alkyl; (4) C 1  -C 4  alkoxy; (5) trifluoromethoxy; (6) cyano; (7) nitro; (8) C 1  -C 4  haloalkyl; (9) R b  SO n  -- wherein n is the intger 0, 1 or 2; and R b  is (a) C 1  -C 4  alkyl; (b) C 1  -C 4  alkyl substituted with halogen or cyano; (c) phenyl; or (d) benzyl; (10) --NR c  R d  wherein R c  and R d  independently are hydrogen or C 1  -C 4  alkyl; (11) R e  C(O)-- wherein R e  is C 1  -C 4  alkyl or C 1  -C 4  alkoxy; or (12) --SO 2  NR c  R d  wherein R c  and R d  are as defined; and (13) --N(R c )C(O)R d  wherein R e  and R d  are as defined and their salts are useful as herbicides.

BACKGROUND OF THE INVENTION

3-(2-Nitro,5-chlorobenzoyl-2,4-pentanedione is taught in J. Chem. Soc.,Chem. Commun., 19 782-3 (1975). No use for this compound is taught.3-(2-Nitrobenzoyl)-2,4-pentanedione is taught in Tetrahedron, 39(19),2933-8 (1982). No use for this compound is taught.

DESCRIPTION OF THE INVENTION

This invention relates to 1-phenyl-3-alkyl-1,3-propanediones and theiruse as herbicides.

One embodiment of this invention is an herbicidal composition comprisingan herbicidally active 1-phenyl-3-alkyl-1,3-propanediones and an inertcarrier therefor. The 2-position of the 1,3-propanedione moiety issubstituted, preferably with a C₁ -C₄ alkyl C(O)-- or C₁ -C₄ alkoxyC(O)-- group. The benzoyl moiety can be substituted, preferably with thegroups hereinafter recited.

Also embodied within the scope of this invention are novel compoundshaving the following structural formula ##STR2## wherein

R is halogen; C₁ -C₂ alkyl, preferably methyl; C₁ -C₂ alkoxy, preferablymethoxy; nitro; cyano; C₁ -C₂ haloalkyl, preferably trifluoromethyl; orR^(a) SO_(n) -- wherein n is 0 or 2, preferably 2 and R^(a) is C₁ -C₂alkyl, preferably methyl. Preferably, R is chlorine, bromine, C₁ -C₂alkyl, C₁ -C₂ alkoxy, trifluoromethyl, cyano, nitro, C₁ -C₂ alkylthio orC₁ -C₂ alkylsulfonyl; more preferably chlorine, nitro, methyl,trifluoromethyl or methylsulfonyl; and

R¹ is C₁ -C₄ alkyl, preferably methyl;

R² is C₁ -C₄ alkyl, preferably methyl, or C₁ -C₄ alkoxy, preferably,ethoxy;

R³ and R⁴ independently are (1) hydrogen, (2) halogen, preferablychlorine, fluorine or bromine; (3) C₁ -C₄ alkyl, preferably methyl; (4)C₁ -C₄ alkoxy, preferably methoxy; (5) trifluoromethoxy; (6) cyano; (7)nitro; (8) C₁ -C₄ haloalkyl, more preferably trifluoromethyl; (9) R^(b)SO_(n) -- wherein n is the integer 0, 1 or 2, preferably 2; and R^(b) is(a) C₁ -C₄ alkyl, preferably methyl; (b) C₁ -C₄ alkyl substituted withhalogen or cyano, preferably chloromethyl, trifluoromethyl orcyanomethyl; (c) phenyl; or (d) benzyl; (10) --NR^(c) R^(d) whereinR^(c) and R^(d) independently are hydrogen or C₁ -C₄ alkyl; (11) R^(e)C(O)-- wherein R^(e) is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; (12) --SO₂ NR^(c)R.sup. d wherein R^(c) and R^(d) are as defined; or (13)--N(R^(c))C(O)R^(d) wherein R^(e) and R^(d) are as defined.

Preferably R³ is in the 3-position. More preferably R³ is hydrogen,chlorine, fluorine, trifluoromethyl, cyano, C₁ -C₄ alkoxy or C₁ -C₄thioalkyl. Most preferably, R³ is hydrogen. Preferably R⁴ is in the4-position. Most preferably R⁴ is halogen, cyano, trifluoromethyl, orR^(b) SO₂ wherein R^(b) is C₁ -C₄ alkyl, preferably methyl or C₁ -C₄haloalkyl, preferably chloromethyl, difluoromethyl or trifluoromethyl.

The term "C₁ -C₄ alkyl" includes methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, isobutyl and t-butyl. The term "halogen" includeschlorine, bromine, iodine and fluorine. The terms "C₁ -C₄ alkoxy"includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy,isobutoxy and t-butoxy. The term "C₁ -C₄ haloalkyl" includes the alkylgroups defined above under C₁ -C₄ alkyl in which one or more hydrogen isreplaced by chlorine, bromine, iodine or fluorine.

Salts of the above-described compounds (as defined hereinafter) areincluded within the scope of the instant invention.

The compounds of this invention can have the following four structuralformulae because of tautomerism: ##STR3## wherein R, R¹, R², R³ and R⁴are as defined above.

The circled proton on each of the four tautomers is reasonably labile.These protons are acidic and can be removed by reaction with a base toform a salt having an anion of the following four resonance forms:##STR4## wherein R, R¹, R², R³ and R⁴ are as defined above.

Examples of cations of these bases are inorganic cations such as alkalimetals, e.g. lithium, sodium and potassium; the alkaline earth metals,e.g. calcium and magnesium or ammonium or organic cations such assubstituted ammonium, sulfonium, sulfoxonium or phosphonium wherein thesubstituents are aliphatic or aromatic groups.

Those skilled in the art will recognize in considering the salts of thisinvention that varying degrees of association between the anion andcation will exist depending upon the nature of the cation. In someinstances with a suitable cation, such as copper, the salt can exist ina chelated form.

The compounds of this invention and their salts are active herbicides ofa general type. That is, they are herbicidally effective against a widerange of plant species. The method of controlling undesirable vegetationof the present invention comprises applying an herbicidally effectiveamount of the above-described compounds or their salts to the area wherecontrol is desired.

The compounds of the present invention can be prepared by the followinggeneral method. ##STR5##

Generally, mole amounts of the dione, magnesium ethoxide, andsubstituted benzoyl chloride are used. The dione and magnesium ethoxideare combined in a solvent such as ethyl ether and heated at reflux for 1hour. The benzoyl chloride is then slowly added, and the reactionmixture is heated at reflux for another 0.5-1 hour. The reaction productis worked up by conventional techniques.

The above described substituted benzoyl chlorides can be prepared fromthe corresponding substituted benzoic acids according to the teaching ofReagents for Organic Synthesis, Vol. I, L. F. Fieser and M. Fieser, pp.767-769 (1967). ##STR6## wherein R, R³ and R⁴ are as previously defined.

The substituted benzoic acids can be prepared by a wide variety ofgeneral methods according to the teaching of The Chemistry of CarboxylicAcids and Esters, S. Patai, editor, J. Wiley and Sons, New York, N.Y.(1969) and Survey of Organic Synthesis, C. A. Buehler and D. F. Pearson,J. Wiley and Sons, (1970).

The following are three representative examples of the methods describedtherein. ##STR7## wherein R, R³ and R⁴ are as previously defined.

In reaction (a) the substituted benzonitrile is heated to reflux inaqueous sulfuric acid for several hours. The mixture is cooled and thereaction product is isolated by conventional techniques. ##STR8##wherein R, R³ and R⁴ are as previously defined.

In reaction (b) the substituted acetophenone is heated to reflux forseveral hours in an aqueous hypochlorite solution. The mixture is cooledand the reaction product is isolated by conventional techniques.##STR9## wherein R, R³ and R⁴ are as previously defined.

In reaction (c) the substituted toluene is heated to reflux in anaqueous solution of potassium permanganate for several hours. Thesolution is then filtered and the reaction product is isolated byconventional techniques.

The following example teaches the synthesis of a representative compoundof this invention.

EXAMPLE 1 3-(2,4-Dichlorobenzoyl)-2,4-pentanedione ##STR10##

A mixture of magnesium ethoxide (22.9 g, 0.2 moles) 2,4-pentanedione(20.0 g, 0.2 moles), and ether (150 ml) was heated at reflux for 1 hour.2,4-Dichlorobenzoyl chloride (41.9 g, 0.2 mole) in ether (50 ml) wasadded to the mixture over a period of 15 minutes, and the resultantmixture was heated at reflux for an additional 0.5 hour. After cooling,the reaction mixture was poured into 200 ml of 10% sulfuric acid. Theether layer was separated and stirred with 250 ml of 5% copper (II)acetate. The resulting copper salt was filtered, washed with ether, andstirred with 6N hydrochloric acid to destroy the salt. The acidicaqueous solution was extracted with ether. The ether extract was washedwith saturated sodium chloride, dried over anhydrous magnesium sulfate,and concentrated under vacuum yielding 21 g of the desired product as ayellow oil. It was identified as such by nuclear magnetic resonancespectroscopy, infrared spectroscopy, and mass spectroscopy.

The following is a table of certain selected compounds that arepreparable according to the procedure described hereto. Compound numbersare assigned to each compound and are used throughout the remainder ofthe application.

                  TABLE I                                                         ______________________________________                                         ##STR11##                                                                                                             n.sub.D.sup.30 /                     Cmpd. No.                                                                             R      R.sup.1 R.sup.2                                                                             R.sup.3                                                                           R.sup.4 m.p. °C.                      ______________________________________                                        .sup. 1.sup.a                                                                         Cl     CH.sub.3                                                                              CH.sub.3                                                                            H   4-Cl    oil                                  2       NO.sub.2                                                                             CH.sub.3                                                                              CH.sub.3                                                                            H   H       oil                                  3       NO.sub.2                                                                             CH.sub.3                                                                              CH.sub.3                                                                            H   4-CF.sub.3                                                                            79-83                                4       Cl     CH.sub.3                                                                              CH.sub.3                                                                            H   4-SO.sub.2 CH.sub.3                                                                   oil                                  5       NO.sub.2                                                                             i-C.sub.3 H.sub.7                                                                     i-C.sub.3 H.sub.7                                                                   H   4-CF.sub.3                                                                            semi-solid                           .sup. 6.sup.b                                                                         Cl     CH.sub.3                                                                              C.sub.2 H.sub.5 O                                                                   H   4-Cl    97-99                                7       Cl     CH.sub.3                                                                              C.sub.2 H.sub.5 O                                                                   H   4-Cl    oil                                  .sup. 8.sup.b                                                                         Cl     CH.sub.3                                                                              C.sub.2 H.sub.5 O                                                                   H   4-SO.sub.2 CH.sub.3                                                                   221 (dec.)                           .sup.  9.sup.c                                                                        Cl     CH.sub.3                                                                              C.sub.2 H.sub.5 O                                                                   H   4-Cl    220 (dec.)                           10      Cl     CH.sub.3                                                                              C.sub.2 H.sub.5 O                                                                   H   4-SO.sub.2 CH.sub.3                                                                   oil                                  ______________________________________                                         .sup.a prepared in Example 1.                                                 .sup.b sodium salt of compound                                                .sup.c ammonium salt of compound                                         

HERBICIDAL SCREENING TESTS

As previously mentioned, the herein described compounds produced in theabove-described manner are phytotoxic compounds which are useful andvaluable in controlling various plant species. Selected compounds ofthis invention were tested as herbicides in the following manner.

Pre-emergence herbicide test: On the day preceding treatment, seeds ofseven different weed species are planted in loamy sand soil inindividual rows using one species per row across the width of a flat.The seeds used are green foxtail (FT) (Setaria viridis), watergrass (WG)(Echinochloa crusgalli), wild oat (WO) (Avena fatua), annualmorningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilontheophrasti), Indian mustard (MD) (Brassica juncea), and yellow nutsedge(YNG) (Cyperus esculentus). Ample seeds are planted to give about 20 to40 seedlings per row, after emergence, depending upon the size of theplants.

Using an analytical balance, 600 milligrams (mg) of the compound to betested are weighed out on a piece of glassine weighing paper. The paperand compound are placed in a 60 milliliter (ml) wide-mouth clear bottleand dissolved in 45 ml of acetone or substituted solvent. Eighteen ml ofthis solution are transferred to a 60 ml wide-mouth clear bottle anddiluted with 22 ml of a water and acetone mixture (19:1) containingenough polyoxyethylene sorbitan monolaurate emulsifier to give a finalsolution of 0.5% (v/v). The solution is then sprayed on a seeded flat ona linear spray table calibrated to deliver 80 gallons per acre (748L/ha). The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperatureof 70° to 80° F. and watered by sprinkling. Two weeks after treatment,the degree of injury or control is determined by comparison withuntreated check plants of the same age. The injury rating from 0 to 100%is recorded for each species as percent control with 0% representing noinjury and 100% representing complete control.

The results of the tests are shown in the following Table II.

                  TABLE II                                                        ______________________________________                                        Pre-Emergence Herbicidal Activity                                             Application Rate - 4.48 kg/ha                                                 Cmpd.                                                                         No.    FT     WG      WO   AMG    VL   MD    YNG                              ______________________________________                                        1      60     --       0   10      0    20    0                               2      100     70     60   10      20   70    0                               3      100    100     70   50     100  100   80                               4      85      85     20   35     100  100   90                                5*     0      5       0   60     100  100   15                               6      60     100      5    0      30   50    0                               7      10      95      5    0      0    10    0                               8      60     100     20   40     100  100   80                               9      40     100      5   10      50   50   30                               10     80     100     30   10     100  100   80                               ______________________________________                                         A blank (--) indicates that the weed was not tested.                          *Tested at 1,12 kg/ha.                                                   

Post-Emergence Herbicide Test: This test is conducted in an identicalmanner to the testing procedure for the pre-emergence herbicide test,except the seeds of the seven different weed species are planted 10-12days before treatment. Also, watering of the treated flats is confinedto the soil surface and not to the foliage of the sprouted plants.

The results of the post-emergence herbicide test are reported in TableIII.

                  TABLE III                                                       ______________________________________                                        Post-Emergence Herbicidal Activity                                            Application Rate - 4.48 kg/ha                                                 Cmpd.                                                                         No.    FT     WG      WO   AMG    VL   MD    YNG                              ______________________________________                                        1      20     20       0   20     100   65   10                               2      20     25      40   20      50   15   15                               3      80     75      50   40     100  100   55                               4      80     70      40   30     100  100   65                                5*    30     20       0   45      25   20   10                               6       0      0       0    5      5    5     0                               7       5     10      10   10     100  100    0                               8      90     60      10   80     100  100   30                               9      10     20      10   40     100  100    0                               10     50     60      20   95      95   95   40                               ______________________________________                                         A blank (--) indicates the weed was not tested.                               *Tested at 1.12 kg/ha.                                                   

The compounds of the present invention and their salts are useful asherbicides and can be applied in a variety of ways at variousconcentrations. In practice, the compounds or salts are formulated intoherbicidal compositions, by admixture, in herbicidally effectiveamounts, with the adjuvants and carriers normally employed forfacilitating the dispersion of active ingredients for agriculturalapplications, recognizing the fact that the formulation and mode ofapplication of a toxicant may affect the activity of the materials in agiven application. Thus, these active herbicidal compounds or salts canbe formulated as granules of relatively large particle size, as wettablepowders, as emulsifiable concentrates, as powdery dusts, as flowables,as solutions or as any of several other known types of formulations,depending upon the desired mode of application. These formulations maycontain as little as about 0.5% to as much as about 95% or more byweight of active ingredient. A herbicidally effective amount dependsupon the nature of the seeds or plants to be controlled and the rate ofapplication varies from about 0.01 to approximately 10 pounds per acre,preferably from about 0.02 to about 4 pounds per acre.

Wettable powders are in the form of finely divided particles whichdisperse readily in water or other dispersants. The wettable powder isultimately applied to the soil either as a dry dust or as a dispersionin water or other liquid. Typical carriers for wettable powders includefuller's earth, kaolin clays, silicas and other readily wet organic orinorganic diluents. Wettable powders normally are prepared to containabout 5% to about 95% of the active ingredient and usually also containa small amount of wetting, dispersing, or emulsifying agent tofacilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which aredispersible in water or other dispersant, and may consist entirely ofthe active compound or salt with a liquid or solid emulsifying agent, ormay also contain a liquid carrier, such as xylene, heavy aromaticnaphthal, isophorone and other non-volatile organic solvents. Forherbicidal application, these concentrates are dispersed in water orother liquid carrier and normally applied as a spray to the area to betreated. The percentage by weight of the essential active ingredient mayvary according to the manner in which the composition is to be applied,but in general comprises about 0.5% to 95% of active ingredient byweight of the herbicidal composition.

Granular formulations wherein the toxicant is carried on relativelycoarse particles, are usually applied without dilution to the area inwhich suppression of vegetation is desired. Typical carriers forgranular formulations include sand, fuller's earth, attapulgite clay,bentonite clays, montmorillonite clay, vermiculite, perlite and otherorganic or inorganic materials which absorb or which may be coated withthe toxicant. Granular formulations normally are prepared to containabout 5% to about 25% of active ingredients which may includesurface-active agents such heavy aromatic naphthas, kerosene or otherpetroleum fractions, or vegetable oils; and/or stickers such asdestrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agriculturalformulations include, for example, the alkyl and alkylaryl sulfonatesand sulfates and their salts; polyhydric alcohols; polyethoxylatedalcohols; esters and fatty amines; and other types of surface-activeagents, many of which are available in commerce. The surface-activeagent, when used, normally comprises from 0.1% to 15% by weight of theherbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredient withfinely divided solids such as talc, clays, flours and other organic andinorganic solids which act as dispersants and carriers for the toxicant,are useful formulations for soil-incorporating application.

Pastes, which are homogeneous suspensions of a finely divided solidtoxicant in a liquid carrier such as water or oil, are employed forspecific purposes. These formulations normally contain about 5% to about95% of active ingredient by weight, and may also contain small amountsof a wetting, dispersing or emulsifying agent to facilitate dispersion.For application, the pastes are normally diluted and applied as a sprayto the area to be affected.

Other useful formulations for herbicidal applications include simplesolutions of the active ingredient in a dispersant in which it iscompletely soluble at the desired concentration, such as acetone,alkylated naphthalenes, xylene and other organic solvents. Pressurizedsprays, typically aerosols, wherein the active ingredient is dispersedin finely-divided form as a result of vaporization of a low boilingdispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention can be applied to theplants in the conventional manner. Thus, the dust and liquidcompositions can be applied to the plant by the use of power-dusters,boom and hand sprayers and spray dusters. The compositions can also beapplied from airplanes as a dust or a spray or by rope wick applicationsbecause they are effective in very low dosages. In order to modify orcontrol growth of germinating seeds or emerging seedlings, as a typicalexample, the dust and liquid compositions can be applied to the soilaccording to conventional methods and can be distributed in the soil toa depth of at least 1/2 inch below the soil surface. It is not necessarythat the phytotoxic compositions be mechanically admixed with the soilparticles since these compositions can also be applied merely byspraying or sprinkling the surface of the soil. The phytotoxiccompositions of this invention can also be applied by addition toirrigation water supplied to the field to be treated. This method ofapplication permits the penetration of the compositions into the soil asthe water is absorbed therein. Dust compositions, granular compositionsor liquid formulations applied to the surface of the soil can bedistributed below the surface of the soil by conventional means such asdiscing, dragging or mixing operations. In the following examples theherbicidal compound can be substituted with the herbicidal salt of thecompound.

    ______________________________________                                        General Formula with Ranges                                                                    Specific Formula                                             ______________________________________                                        EMULSIFIABLE CONCENTRATE FORMULATIONS                                         Herbicidal compound                                                                        5-55    herbicidal compound                                                                            24                                      surfactant(s)                                                                              5-25    proprietary blend of oil-                                                                      10                                      solvent(s)   20-90   soluble sulfonates and                                                100%    polyoxyethylene ethers                                                        polar solvent    27                                                           petroleum hydrocarbon                                                                          39                                                                            100%                                    WETTABLE POWDER FORMULATIONS                                                  herbicidal compound                                                                        3-90    herbicidal compound                                                                            80                                      wetting agent                                                                              0.5-2   sodium dialkyl naphthalene                                                                     0.5                                     dispersing agent                                                                           1-8     sulfonate                                                diluent(s)   8.5-87  sodium lignosulfonate                                                                          7                                                    100%    attapulgite clay 12.5                                                                          100%                                    EXTRUDED GRANULAR FORMULATIONS                                                herbicidal compound                                                                        1-20    herbicidal compound                                                                            10                                      binding agent                                                                              0-10    lignin sulfonate  5                                      diluent(s)   70-99   calcium carbonate                                                                              85                                                   100%                     100%                                    FLOWABLE FORMULATIONS                                                         herbicidal compound                                                                        20-70   herbicidal compound                                                                            45                                      surfactant(s)                                                                              1-10    polyoxyethylene ether                                                                          5                                       suspending agent(s)                                                                        0.05-1  attagel          0.05                                    antifreeze agent                                                                           1-10    propylene glycol 10                                      antimicrobial agent                                                                        1-10    1,2-benzisothiazoline-3-one                                                                    0.03                                    antifoam agent                                                                             0.1-1   silicone defoamer                                                                              0.02                                    solvent      7.95-   water            39.9                                                 77.85                    100%                                                 100%                                                             ______________________________________                                    

When salts are used as the active ingredient in the herbicidalcompositions of this invention it is recommended to use salts that areagriculturally acceptable.

The phytotoxic compositions of this invention can also contain otheradditives, for example, fertilizers, other herbicides and otherpesticides, used as adjuvant or in combination with any of theabovedescribed adjuvants. Fertilizers useful in combination with theactive ingredients include, for example, ammonium nitrate, urea andsuperphosphate.

What is claimed is:
 1. The method of controlling undesirable vegetation comprising applying to the area where control is desired, an herbicidally effective amount of a compound having the formula ##STR12## wherein R is halogen; C₁ -C₂ alkyl; C₁ -C₂ alkoxy; nitro; C₁ -C₂ haloalkyl; or R^(a) SO_(n) -- wherein n is 0 or 2 and R^(a) is C₁ -C₂ alkyl;R¹ is C₁ -C₄ alkyl; R² is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; R³ and R⁴ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C₁ -C₄ haloalkyl; (8) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen; (c) phenyl; or (d) benzyl and their salts.
 2. The method of claim 1 wherein R is chlorine, bromine, methyl, methoxy, nitro, trifluoromethyl, or methylsulfonyl; R¹ is C₁ -C₄ alkyl; R² is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; and R³ and R⁴ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C₁ -C₄ haloalkyl; (8) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen; (c) phenyl; or (d) benzyl.
 3. The method of claim 1 wherein R³ and R⁴ are independently hydrogen; chlorine; fluorine; bromine; methyl; C₁ -C₄ alkoxy; trifluoromethoxy; nitro; trifluoromethyl; R^(b) SO_(n) -- wherein n is the integer 0 or 2 and R^(b) is methyl, chloromethyl, trifluoromethyl, ethyl, or n-propyl; and R³ is in the 3-position and R⁴ is in the 4-position.
 4. The method of claim 1 wherein R³ is hydrogen and R⁴ is hydrogen, chlorine, bromine, fluorine, trifluoromethyl or R^(b) SO₂ wherein R^(b) is C₁ -C₄ alkyl or C₁ -C₄ haloalkyl.
 5. The method of claim 1 wherein R is nitro, R¹ is methyl; R² is methyl; R³ is methyl; R³ is hydrogen; and R⁴ is 4-trifluoromethyl.
 6. The method of claim 1 wherein R is chlorine; R¹ is methyl; R² is methyl; R³ is hydrogen; and R⁴ is 4-SO₂ CH₃.
 7. The method of claim 1 wherein R is chlorine; R¹ is methyl; R² is ethoxy; R³ is hydrogen and R⁴ is 4-SO₂ CH₃.
 8. The method of claim 1 wherein R³ is hydrogen.
 9. The method of claim 2 wherein R³ is hydrogen.
 10. The herbicidal composition comprising a herbicidally active 1-phenyl-3-alkyl-1,3-alkanedione compound of the formula ##STR13## wherein R is halogen; C₁ -C₂ alkyl; C₁ -C₂ alkoxy; nitro; C₁ -C₂ haloalkyl; or R^(a) SO_(n) -- wherein n is 0 or 2 and R^(a) is C₁ -C₂ alkyl;R¹ is C₁ -C₄ alkyl; R² is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; R³ and R⁴ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C₁ -C₄ haloalkyl; (8) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen; (c) phenyl; or (d) benzyl; or their salts and an inert carrier therefor with the proviso that when R is nitro both R3 and R4 can not be hydrogen.
 11. The composition of claim 10 wherein R is chlorine, bromine, methyl, methoxy, nitro, trifluoromethyl, or methylsulfonyl; R¹ is C₁ -C₄ alkyl; R² is C₁ -C₄ alkyl or C₁ -C₄ alkoxy; and R³ and R⁴ independently are (1) hydrogen; (2) halogen; (3) C₁ -C₄ alkyl; (4) C₁ -C₄ alkoxy; (5) trifluoromethoxy; (6) nitro; (7) C₁ -C₄ haloalkyl; (8) R^(b) SO_(n) -- wherein n is the integer 0, 1 or 2; and R^(b) is (a) C₁ -C₄ alkyl; (b) C₁ -C₄ alkyl substituted with halogen; (c) phenyl; or (d) benzyl.
 12. The composition of claim 11 wherein R³ and R⁴ are independently hydrogen; chlorine; fluorine; bromine; methyl; C₁ -C₄₄ alkoxy; trifluoromethoxy; nitro; trifluoromethyl; R^(b) SO_(n) -- wherein n is the integer 0 or 2 and R^(b) is methyl, chloromethyl, trifluoromethyl, ethyl, or n-propyl; and R³ is in the 3-position and R⁴ is in the 4-position.
 13. The composition of claim 11 wherein R³ is hydrogen and R⁴ is hydrogen, chlorine, bromine, fluorine, trifluoromethyl or R^(b) SO₂ wherein R^(b) is C₁ -C₄ alkyl or C₁ -C₄ haloalkyl.
 14. The composition of claim 10 wherein R is nitro, R¹ is methyl; R² is methyl; R³ is hydrogen; and R⁴ is 4-trifluoromethyl.
 15. The composition of claim 10 wherein R is chlorine; R¹ is methyl; R² is methyl; R³ is hydrogen; and R⁴ is 4-SO₂ CH₃.
 16. The composition of claim 10 wherein R is chlorine; R¹ is methyl; R² is ethoxy; R³ is hydrogen and R⁴ is 4-SO₂ CH₃.
 17. The compositions of claim 10 wherein R³ is hydrogen.
 18. The compositions of claim 10 wherein R³ is hydrogen. 